Throat plate for overedge sewing machine



Aug. 13, 1963 J. M. WASHBURN THROAT PLATE FOR OVEREDGE SEWING MACHINE 2sheets-sheet 1 Filed Sept. 6. 1961 Z JX J 25% Wv-M Aug. 13, 1963 J. M.WASHBURN THROAT PLATE FOR OVEREDGE SEWING MACHINE Filed Sept. 6, 1961 2Sheets-Sheet 2 Jflll/nM Basil/burn United States Patent O" .Thisinvention relates to throat plates employed in overedge sewing machines,and more particularly to an improved stitch finger assembly forloveredge machines employing two needles in side by side relationship.

Inthe formation of certain types of seams, two rows of needle threadloops are placed in the Work material along lines parallel to the workmaterial edgeand a third thread is manipulated by the loopermechanism ofthe machine to be interlooped with both series of needle thread loops.To accomplish this operatiom in certain seams it is necessary that themachine be provided with two stitch fingers, one of which extendsbetween the two rows of needle thread loops. In the formation of theseam, the needle whichforms the row of loops remote from the workmaterial edge carries its thread downwardly through the fabric to apoint below the lower edge of the last mentioned stitch finger intooperative relationship with the looper which carries the loop laterallybeneath the stitch finger. As the material is fed through the machine,the loop slides longitudinally along the stitch finger until itslips oilthe distal end of the finger.

In many types of seams; the lateral spacing between the two rows ofneedle thread loops is quite small, and since the inner stitch fingermust project between the two rows of loops" While permitting clearanceso that the needles can pass down on opposite sides of the stitchfinger, the finger must, of necessity be of relatively small width. Atthe same time, because of the high speed of feed, 'thestitch finger musthave a reasonable length, thus resulting in a requirement that thestitch finger be relativelylong, thin and cantilevered from the throatplate in order that the stitches may slip freely from its distal end.During the formation of the ,stitches, the needle thread loops are drawntaut while they are still on the stitch finger.

This action exerts a pull on the stitch finger :which, because of thedesign requirements referred toabove, subjects the finger to vibrationwhen in use. Thus,the stitch finger, because of its dimensions, isreadily subjected to damage and, if formed integrally with the throatplate, is a primary cause of damage requiring replacement of i the.complete throat plate. Previous efforts to provide thnoat plateconstruction in which the stitch finger may bereplaced withoutdiscarding the entire plate have not proved completely satisfactorybecause of difficulties encountered in providing-satisfactory means forsecuring the finger on the plate with sullicient rigidity to resistthetendency machine'isoperated. I fA'ccordingly, isan object of thepresentinvention to provide a throat plate for i use ill a two needle overedgesewingrn-achine having replaceable stitch finger'which ofthe finger tovibrate whenthe rn'ay be rigidly secured to the, throat plate.

5 In the achievement of the foregoing, and other objects, a throat plateassembly is constructed with an upwardly opening groove of uniform widthand varying depth formed in the upper surface of the plate. The innerstitch finger is separately formed from sheet material having athickness which provides a sliding fit between the sidewalls of thegroove in the throat plate. At one end, the stitch finger is formed witha finger portion having a maximum thickness at its base substantiallyequal to the thickness of the throat plate and tapering toward thedistal or free end of the finger to permit thread loops 3,100,469Patented Aug. 13, 1963 2 to slide easily from the finger portion. The.opposite end portion of the stitch finger -is formed as a shank or tangwhose vertical dimension is somewhat less than the depth of the groovein the throat plate; The groove in the throat plate is formed with afiat bottom portion whichextends from the inner end of the needlereceiving slot within which the stitch finger islocated lengthwise ofthe throat plate to terminate at oneend of a depressed intermediatebottom portion of the. throat plate groove. The con-figuration of thestitch finger and bottom portion of the groove is such that when itstang is initially placed in the groove, the lower surface of the tangcontacts the groove only at two points, one at the forward end of theflat portion adjacent the inner end of the needle receiving slot and theother point of contact being near the end of the depressed intermediateportion of the groove remote from the flat portion. .At a locationlongitudinally of the slot substantially midwaybetween the inner end ofthe flat portion and this latter point of contact, a bore extendsthrough the body. of the throat plate traversely across the slot. Awedging pin having a tapered wedge section is received within this boreand its tapered portion is adapted to engage a notch in the uppersurface of the tang so that when the pin is driven laterally across theslot, the tapered portion of the pin forces the tang portion downwardlyand rearwardly within the groove to seat the forward end o-f-the tangportion in faceto face contact with the flat portion, therebyresiliently locking the stitch finger in position upon the plate. Thelower portion of the base of the finger portion of the stitch finger isformed with an upwardly and forwardly inclined shoulder surface whichextends upwardly from the lower side' of the stitch finger and is hookedover the edge surface of the throat plate at the inner end of. the slot.

The, rearward and downward wedging action exerted on the stitch fingertang by the wedge pin tends to move this shoulder toward engagement withthe oppbsed surface of the throat plate, thus exerting a firmlongitudinal locking action on the st-itchfinger. The downwardyfiexingaction flexes the relatively large ,ve'rtical depth. of thestitch fingerwhich serves to increase the rigidity of the finger'when the machine-isin operation. .F

\ of FIG. 1, showing the. assembly without the removable stitch fingeror wedgingpiny: BIG. 4 is a cross-sectional view similar to FIG. 3*showingthe remov ablestitch finger in :place within its .re'-

ceivinggroove prior tofthe placementof the wedging pin,

and." A

l BIG. is a cross-sectional ilietwaisimilar toFIG; 3 showingthe parts intheirrassentbled relationship. Referring first to FIG; 1, there is showna throat plate lthrformed with a feed dog receiv-' a relieved feed dogreceiving recess 14 which accommodate motion. of the feed dogs ofdesignated generally ing opening 12 and the machine ina well knownmannerto feed work material indicated in broken line at W. through themachine in the direction; indicated by arrow 16. Throat plate 10 isboredas at 18 to receive a screw whichis employed to mount the plate upon themachine in the general fashion indicated in my prior Patent No.2,233,088, granted February 25, 1941, to which reference may also be hadfor the general relationship of throat plate 10 in an overedge sewingmachine.

the 1 assembly of dog opening 12 as at 42.

Immediately to therear (the terms ifront and rear refer to the directionof feed, the direction of feed moving the work material from front torear) a first stitch finger 24 is formed as an integnal part of throatplate 10. The inner edge 22 of stitch finger 26 is lo cated in spacedparallel relationship to aside edge 24 on throat plate edgesf22' and 24defining the longitudinal sidewalls of aneedle receiving slot whoseinner I end is defined by a traversely extending edge 25' on throatplate 10. i The transverse width" of the needle re-' ceiving slot issuch that thread carrying needles of ah overedge sewing machine uponwhich the throat plate is f employed pass'vertically through the slot atlocations indicated in FIG. '1 at 28 and 30. i V

A groove designated generally 32 is (formed in the upper surface ofthroatplate 10 and, as best seen in FIG. 1, extends substantiallyentirely across the upper.

surface of throat plate 10 from transverse edge 26 in longitudinal[alignment with the longitudinal center line of the needle receivingslot. ,Groove 32 is: of uniform width and has spaced parallel verticalsidewalls.

. The configuration of the lower wall of groove 32 is best seen in FIGS.3 through 5. At the end of groove 32 "adjacent totransverse edge 26, thelower wall of groove t 32 is ionmed with a flat downwardly land inwardlyinclined portion 34. At its inner end, fiat portion 34 terminates at oneend of an intermediate portion 36 which, since it defines the maximumdepth of the groove 32 relative to the upper surface of throat plate 10,will he referred to as a depressed portion. Throat plate 1%} is formedwith a transverse bore 3 8 which, as best seen in FIGS. 1 land 2,extends from the sidewall lll of throat I right to left as viewed inFIG. 2, tapered portion 68 passesthrou gh notch 64 and enters thatportion of bore plate 10 transversely across groove 32 to open into feed7 dog opening 12. Preferably, for reasons discussed below, bore 38 isextended to similarly pass through that portion of throat plate 10 onthe opposite side 'offeed .--Groove 32 and bore 38 are formed in throatplate 10 for the purpose of locating and securing a stitch fingerelement designated generally 44 in position upon the throat plate;Stitchtinger element 44 is constructed from plate or sheet materialhaving athickness adapted to ibe: snuglyreceived between the: lverticalsidewalls sliding'element 4a to the right as viewed in FIG.'4 untilshoulder 5% contacts the lower portion 62 of transverse edge 26 of thethroat plate. Dower portion 62 of edge 26 is inclined upwardly andforwardly at a slightly greater angle than shoulder 50. A notch 64 iscut into the upper edge of tang portion 48 at a location such that whenshoulder 5t contacts edge 62, notch '64 is disposed longitudinallywithin groove 32 in alignment with bore 38.

A wedge pin 66 is received within bore 38 a loose drive fit. The innerend of pin 66 is tapered as at'68 (FIG. 2) so that as pin 66' is driveninto bore 38 from 38 to the left of groove'32 aswiewedin'FIG. 2. Furtherdriving movement of pin 66 to the left'as' viewed in FIG;

4 position until its upper edge'7il is moved into substantialparallelism with the upper surface of stitch finger 20. The maximumdepth of notch 64 is located somewhat to the left of the center of bore38 as viewed in FIGS. 4 and 5 and hence the wedging action of taperedportion 68 of pin 66 is also applied against the inclined right handportion of notch 64- to urge stitch fingerelement 44 to the left at thesame time that tang portion 14.8 is flexed downwardly by the-pin. Thisaction thus also resiliently wedges shoulder 50 toward lower edgeportion 62 of transverse edge '26. I a e I The foregoing constructionachieves a central or inner stitch finger on =th'roat plate v1t) whichis held in position extremely rig-idly by virtue of the wedging actionof of groove 32 andis formed atone-end with a stitch finger portion 46,the remainingportion (right hand portion as I viewed in FIGS. 4 and 5)being tormed as an elongate tang 48. I V

. Stitch finger element 44 has its maximum vertical dimension or depthat the base of finger portion 46, at which pointgthe depth of fingerelement'44 issubstantially equal to the vertical thickness of throatplate 10. Since groove I '32 extends downwardly-onlypartially throughthroat plate 10, the base-of finger portion 44 is defined in part by anupwardly andto'rwardly inclined shoulder-50 which extends upwardly from.the tapered -loweredge 52 of finger portion 46 to-merge-t-hrough' asmooth curve into the fiat lower edge 54 of tang portion 48. The upward-and orwardt-aper of. loweredge52 of finger ,por-

tior1=46 facilitates the smooth sliding of thread loops along thestitch. finger ip the direction of work material feed I(toitheleftas:viewediirifFIGSs l and 5) until the thread seeps-suptrom'the'..stitch tinger atit'sdistal end 56.

' As best seen in FIG. 4,: the shape of the lower edge 7 point ofcontact fitl being between the extreme end of tang portion 48 and alocation adjacent the end of depressed portion 36 remote from flatportion 34. Between the two points of contact 58 and 60, thelower'edge54 offstitchiinger element =44 is such that when the element I is placedin groove 32, tang portion 48 contacts the lower.

.; wall of groove 32 only'a-t two points, one point ;58 being located'near the outer end of flat portion 34 and the other pin '66; Iiheapplication of the wcdging force to urge shoulder tightly against edge62 firmlylocks the stitch finger element against longitudinalmovementwithin the slot and the provision of the shoulder at'the'sa'me-t-ime ermits the vertical thickness or depth of the fingerpor-,, tion 46 to he made relatively large to ,further increase therigidity of the operative portion of the stitch linger. Stitch finger.element 44rmay be readily removed by insetting a drive pin through bore42" to drive pin 66 out of V bore 38f I While one embodiment of theinvention has been described in detail, it will be apparentto thoseskilled in the art that the disclosed embodiment may he modifiediTherefore, the foregoing description is to beconsideredj exemplaryratherthan limiting and the true scope of the" I invention is that defined intheiollowing claims. What is claimed is: a

1 For use in an bveredge sewingmachine; a-ithroat plate having a firstfingerthereondefiningan elon-. gate'vneedle receiving slot having spaced'longitudinalvsideedges and a transverse edgedefining. the inner endofsaidslot, said plate having'an upwardly opening groove therev inextending tromfsaidtransver'se edge across the upper,

side or said plate, an elon gate plate-lik'e secondstitch: i

linger member having agstitch linger portion atone end 7 1 V and anelongate tang, said tang being adapted to be re.

ceived within said groove with the opposed sides of said tangengagedwith the side surf-acesv of said groove tolecate said-finger portion ina central longitudinally extend -I ing position within said slot, thelower suhfiace of said of tan-g 48 is vertically spaced above lower wall3436 of groove 32.

Stitch finger element 44 is assembled to throat plate 7 10 by firstplacing tang portion '48 in groove 32 and groove having an intermediateportion thereof depressed relative to the opposed lower surface of saidtang, a shoulder on said member engageablelwith said transverse;

edge, and wedge means engageable between said plate and the uppersurface of said tang at a location above said dep essed portion of saidgroove for flexing said tang port1on downwardly within said groove toresiliently lock said second stitch finger member to said plate.

a stitch finger portion at one end of said second stitch finger member,a tang integral with said stitch finger portion and adapted to bereceived on edge within said groove to locate said stitch fingerport-ion centrally within said slot, a downwardly projecting shoulder onthe lower side of said second stitch finger lmember engageable with.said transverse edge of said slot to longitudinally locate said stitchfinger portion within said slot, the lower surface of said groove havingan intermediate portion therei of depressed relative to the opposedlower edge surface of said tang, and wedge means engageable between saidplate and the upper edge surface of said tang portion a above saiddepressed intermediate portion of said groove for flexing said tangportion downwardly within said groove and urging said shoulder againstsaid transverse edge to lock said second stitch finger member to saidthroat plate.

3. A throat plate as defined in claim 2 wherein said wedge meanscomprises a wedge pin, said throat plate having a bore therethroughextending transversely across said groove and receiving said wedge pin,the upper surface of said tang having a notch therein adapted to engagesaid wedge pin to depress said tang portion and to urge said shoulderagainst said transverse edge upon sliding movement of said pintransversely across said groove.

4. A throat plate as defined in claim 2 wherein the lower surface ofsaid groove includes a flat portion extending between said depressedportion and said transverseedge, the lower surface of said tang beingfiat and 6 adapted to engage said flat portion at a point adjacent saidtransverse edge and to engage the lower surface of said groove at theside of said depressed portion remote from said fiat portion when saidwedge means is disengaged there-from, said wedge means being operable toflex said tang portion downwardly Within said groove until the loweredge of said tang is in face to face contact with said fiat portion ofsaid groove throughout the length of said fiat portion.

5. For use in .an overedge sewing machine; a throat plate having a firststitch finger thereon defining an elongate needle receiving slot open atone end and having spaced longitudinal side edges and a transverse edgedefining the inner end of said slot, said plate having a groove thereinextendingyfrom said transverse edge lengthwise on one side of saidplate, an elongate plate-like second stitch finger member having astitch finger portion at one end and an elongate tang, said tang beingadapted to be received within said groove 'with the opposed sides ofsaid tang engaged with the side surfaces of said groove to locate saidfinger portion in a central longitudinally extending position withinsaid slot, the bottom surface of said groove having an intermediateportion thereof depressed relative to the opposed surface of said tang,a shoulder on said stitch finger member engageable with said transverseedge, and means slideably received Within said plate and engageable withsaid tang at a location opposed to said bottom portion of said groovefor flexing said tang portion in a direction Within said groove toresiliently lock said second stitch finger member to said plate.

References (Iited in the file of this patent Maier Mar. 10, 1931

1. FOR USE IN AN OVEREDGE SEWING MACHINE; A THROAT PLATE HAVING A FIRSTSTITCH FINGER THEREON DEFINING AN ELONGATE NEEDLE RECEIVING SLOT HAVINGSPACED LONGITUDINAL SIDE EDGES AND A TRANSVERSE EDGE DEFINING THE INNEREND OF SAID SLOT, SAID PLATE HAVING AN UPWARDLY OPENING GROOVE THEREINEXTENDING FROM SAID TRANSVERSE EDGE ACROSS THE UPPER SIDE OF SAID PLATE,AN ELONGATE PLATE-LIKE SECOND STITCH FINGER MEMBER HAVING A STITCHFINGER PORTION AT ONE END AND AN ELONGATE TANG, SAID TANG BEING ADAPTEDTO BE RECEIVED WITHIN SAID GROOVE WITH THE OPPOSED SIDES OF SAID TANGENGAGED WITH THE SIDE SURFACES OF SAID GROOVE TO LOCATE SAID FINGERPORTION IN A CENTRAL LONGITUDINALLY EXTENDING POSITION WITHIN SAID SLOT,THE LOWER SURFACE OF SAID GROOVE HAVING AN INTERMEDIATE PORTION THEREOFDEPRESSED RELATIVE TO THE OPPOSED LOWER SURFACE OF SAID TANG, A SHOULDERON SAID MEMBER ENGAGEABLE WITH SAID TRANSVERSE EDGE, AND WEDGE MEANSENGAGEABLE BETWEEN SAID PLATE AND THE UPPER SURFACE OF SAID TANG AT ALOCATION ABOVE SAID DEPRESSED PORTION OF SAID GROOVE FOR FLEXING SAIDTANG PORTION DOWNWARDLY WITHIN SAID GROOVE TO RESILIENTLY LOCK SAIDSECOND STITCH FINGER MEMBER TO SAID PLATE.